'Lecture 5 | Missing Semester Solutions'

pgrep -af sleep

Terminal output:

12345 sleep 1000

pkill -f sleep

sleep 60 &

wait $! | ls

$! refers to the id of the last job. You can change it with the id of another job if you like or use %1 to refer to the first job on the list.

pidwait

pidwait() {
    local pid="$1"

    # Check if a PID was provided
    if [ -z "$pid" ]; then
        echo "Usage: pidwait "
        return 1
    fi

    # Loop until the process is no longer running
    while kill -0 "$pid" 2>/dev/null; do
        sleep 1  # Sleep for 1 second to avoid busy waiting
    done

    echo "Process $pid has completed."
}

.zshrc

alias dc='cd'

You can create a folder in your root directory:

mkdir ~/dotfiles

Then you can use Git to set up version control.
You will see more details on how to use git in the next lecture but if you don't know the basics, here is how to do it:

First you have to install git if you don't already have it.

sudo apt-get install git

Then, you can create a Github account and create a dotfiles repository.
After that, download the remote repository on you local machine using:

git pull [url of your dotfiles repository]

Copy your dotfiles to your dotfiles directory.
When you are ready to save the changes you made, add them to the staging area and make a commit:

git add -A

git commit -m 'my first commit!'

-A adds all files to the staging area, but you can specify each file to add instead
-m '[message]' Specifies the message associated with the commit

You can look at my own dotfiles for some simple configuration example. ChatGPT is also a good tool to find some commonly used configuration.

machine_init.sh

#!/bin/bash

# Install Dotfiles
files="zshrc profile tmux.conf vimrc"

for file in $files; do 
	ln -sf ~/dotfiles/$file ~/.$file

done

You can also setup a script to install zsh, Oh My Zsh! and Zsh plugins

machine_init.sh

#Install Zsh and oh-my-zsh

#Zsh
if ! command -v zsh >/dev/null 2>&1; then
    echo "Zsh not found. Installing Zsh..."
    sudo apt update && sudo apt install -y zsh
else
    echo "Zsh is already installed."
fi

#Oh-my-Zsh
if [ ! -d "$HOME/.oh-my-zsh" ]; then
    echo "Installing Oh My Zsh..."
    # Run the Oh My Zsh installation script
    RUNZSH=no sh -c "$(curl -fsSL https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh)" --unattended
else
    echo "Oh My Zsh is already installed."
fi

# Install zsh plugins

# Define the Oh My Zsh custom plugin directory
ZSH_CUSTOM="$HOME/.oh-my-zsh/custom"
PLUGIN_DIR="$ZSH_CUSTOM/plugins"
AUTOSUGGESTIONS_REPO="https://github.com/zsh-users/zsh-autosuggestions"
SYNTAX_HIGHLIGHTING_REPO="https://github.com/zsh-users/zsh-syntax-highlighting"
FAST_SYNTAX_HIGHLIGHTING_REPO="https://github.com/zdharma-continuum/fast-syntax-highlighting"
AUTOCOMPLETE_REPO="https://github.com/marlonrichert/zsh-autocomplete"

# Create custom plugins directory if it doesn't exist
mkdir -p "$PLUGIN_DIR"

# Function to install a plugin
install_plugin() {
	local repo_url=$1
	local plugin_name=$2
	local plugin_path="$PLUGIN_DIR/$plugin_name"

	echo "Installing $plugin_name..."
	git clone "$repo_url" "$plugin_path"
}

# Install each plugin
install_plugin "$AUTOSUGGESTIONS_REPO" "zsh-autosuggestions"
install_plugin "$SYNTAX_HIGHLIGHTING_REPO" "zsh-syntax-highlighting"
install_plugin "$FAST_SYNTAX_HIGHLIGHTING_REPO" "fast-syntax-highlighting"
install_plugin "$AUTOCOMPLETE_REPO" "zsh-autocomplete"

echo "Zsh, Oh My Zsh, and Zsh plugins installed!"

# Switch shell to zsh
if [ "$SHELL" != "$(which zsh)" ]; then
    echo "Changing default shell to Zsh..."
    chsh -s $(which zsh)
else
    echo "Default shell is already Zsh."
fi

echo "Installation complete!"

You should change the ZSH_CUSTOM variable to $HOME/.zsh/custom if you do not use oh my zsh.

Since we already created the repository in a previous question, all we have to do is

git push [URL]

After starting the server on the vm you should connect your host to the vm with:

SSH -L 9999:localhost:8888 vm

After that you can naviguate (on a browser) to http:localhost:9999

You might have to use python3 instead of python
You should create an alias for python3 is that's the case.

sshd_config

PasswordAuthentification no
PermitRootLogin no

Disabling password authentification forces users to connect using ssh keys. Disabling root logins prevents users from connecting directly as the root. Both increase security.

Install mosh (on both machines):

sudo apt-get install mosh

Then, connect to your vm using mosh:

mosh vm

Disconnect your vm from virtual box and reconnect it again.
As you can see mosh successfully recovers from it instead of crashing.

The -N flag tells SSH not to execute any remote commands. It's used when you only want to establish a connection for port forwarding or tunneling, without running any shell or commands on the remote host.

The -f flag tells SSH to go into the background just before executing the command. When paired with -N, it allows SSH to start the connection, set up the port forwarding, and then run in the background, leaving your terminal free.

To put it all together:

ssh -f -N -L 9999:localhost:8888 vm

Lecture 5

Job control

Terminal Multiplexer

Aliases

Dotfiles

Remote Machines